High-speed impact problems are simulated with smoothed particle hydrodynamics method.Initial smoothing length and nonconforming space between particles in simulation are analyzed.A modified smoothing length approach is put forward.With increase of initial smoothing length, projectile rigidity decreases gradually.A rational range of initial smoothing length is d₀< h₀≤ 1.5d₀.With decrease of space between particles,rigidity of material decreases.With XSPH correction on velocity of a particle,results by nonconforming space between particles agree well with those from identical particle distribution.